Paleoseismological and neotectonic analysis of the Porotoyacu Fault, Sub-Andean Zone of Ecuador
Synopsis
Knowledge of neo-tectonic activity is essential for assessing seismic risk, safeguarding infrastructure, and ensuring sustainable land use. However, the Sub-Andean Zone of Ecuador remains insufficiently studied, particularly the Porotoyacu Fault, which extends 19 km across Tena and Archidona in Napo Province. With a SSW-NE orientation, its seismic activity has only been partially estimated from a single trench analysis, leaving its tectonic behavior poorly understood. This study aims to determine paleo-seismicity and recent tectonic activity using morphotectonic, morphological, and paleoseismological methods, combining satellite imagery with field observations from an anthropogenic outcrop. Evidence includes ruptures, vertical displacements, and seismites such as dykes that disrupt soil layers, confirming Quaternary activity. Three seismic events with magnitudes above Mw 6.1 were identified. Surface deformation and seismites in the upper outcrop units indicate that the Porotoyacu Fault has experienced recent tectonic reactivation, highlighting its potential seismic hazard.
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